AND on Saturday, they walked, in their tens of thousands. From 6am, Sydney was flooded by Catholic pilgrims who walked 10km from North Sydney, over the Harbour Bridge and through the CBD to Randwick Racecourse.

The target; an evening vigil with the Holy Father, Pope Benedict, and a morning mass today to conclude World Youth Day.

While they walked, Pope Benedict had made his historic apology to victims of sexual abuse. Most pilgrims seemed unaware of the apology as they sang songs, danced, chanted ''Benedetto! Benedetto!'' and enjoyed another day of sunshine in the Harbour City.

Most pilgrims had found their allocated sites by nightfall, quite a feat in itself, given the scale of the event, and packed in like sardines, they transformed Randwick into a sea of sleeping bags, tents and a kaleidoscope of national flags.

A cold evening had been forecast, with the temperature tipped to drop to 8 degrees overnight, but no rain expected.

But cold weather was the last thing pilgrims had in mind as they collected generous bags of food, including ready-to-eat meals, biscuits, chocolates and bottles of water and made their way into the venue.

The sleep-out at Randwick was the penultimate event of a week of celebration, prayer, and reflection for Catholic youth.

As many 180,000 pilgrims were expected to make the pilgrimage walk to Randwick.

At 7.30pm, Pope Benedict appeared on the main stage to be welcomed by pilgrims before beginning the vigil that included prayers, hymns and reflections.

Melburnian Julian Butler had been in Sydney for two weeks for World Youth Day.

He said the event was a ''once in a lifetime experience'' to pray with people from all over the world.

''It gives us a sense of the universality of the church.''